The present invention relates to an in-die cover forming method, in which a cover is integrally formed with the surface of a base member in a die, and to a method for manufacturing a product integrated with a cover through the in-die cover forming method.
Interior parts such as side panels and lids of consoles, instrument panels, lids of glove compartments typically have an ornamental surface made of a cover material so that the parts have a quality appearance. When manufacturing such an interior part 80, a resin base member 81 and a cover member 82 are placed in a die 90 as shown in FIG. 3. Then, the die 90 is closed while pressing the cover member 82 against the base member 81 through vacuuming. Consequently, the cover member 82 is integrated with the surface of the base member 81. This method is referred to as the in-die cover forming method. The die 90 used in such a forming method includes an upper die half 90a and a lower die half 90b. The upper die half 90a has a cavity surface that corresponds to the shape of the surface of the base member 81. The lower die half 90b has a cavity surface that corresponds to the shape of the back of the base member 81.
As shown FIG. 3, the interior part 80 has a reinforcing ribs 81c and side walls 81b. When manufacturing the interior part 80 using the die 90, the shape of the back of the base member 81 including the reinforcing ribs 81c and the side walls 81b are caused to conform to the shape of the lower die half 90b as shown in the right half of FIG. 3. In other words, the base member 81 is placed on the lower die half 90b with the position of the base member 81 determined both in the longitudinal and transverse directions. The longitudinal and transverse directions are defined in a plane that is perpendicular to the direction in which the die halves 90a, 90b are moved relative to each other (vertical direction as viewed in FIG. 3).
Subsequently, the cover member 82, which has been heated and softened, is placed on the surface of the base member 81, and the upper die half 90a is placed on the upper surface of the cover member 82. Thereafter, the cover member 82 is drawn from the side of the cavity surface of the lower die half 90b through vacuuming, so that the cover member 82 intimately contacts the base member 81. Finally, the cover member 82 is bonded to the surface of the base member 81 by closing the die 90. Typically, an adhesive is used to bond the cover member 82 to the base member 81.
Generally, the ornamental surface of the interior part 80 has a number of curved shapes to give a quality appearance. It is difficult to integrate the flat cover member 82 with a member having such a three-dimensional configuration. Therefore, defective can be caused. For example, there may be cases where the cover member 82 is displaced from a proper position with respect to the base member 81, or the cover member 82 is partially creased. To deal with such problems, for example, Japanese Laid-Open Patent Publication No. 7-205167 proposes an in-die cover forming method in which a fixation apparatus is used. The fixation apparatus disclosed in the publication No. 7-205167 includes actuators each having an actuation rod at a periphery of an upper die half. When the die is opened, the actuation rods are caused to move toward a lower die half. The actuation rods are moved downward when the die is closed so that the rods press and fix a cover member placed on a lower die half at the periphery. The rods are retracted by the pressure applied by the lower die half as the die is closed.
On the other hand, Japanese Laid-Open Patent Publication No. 2001-179759 discloses a method for forming a product through bonding. In this method, a cover member on the back of which an adhesive layer is formed is pressed against a core having a curved shape. Thereafter, folded portions at the periphery of the cover member are folded back to contact the back of the core. This forming method is characterized by the following features. That is, when pressing the cover member against the surface of the core using the die, water is applied to the back of the folded portions so that the bonding function of the adhesive layer is temporarily lowered. Then, the folded portions are heated so that the portions recover adhesive function, and folded along the back of the core.
As described above, it is difficult to integrate the flat cover member 82 with the base member 81 so as to the cover member 82 conform to the surface of the base member 81 having a three-dimensional shape. Thus, the yield cannot be sufficiently increased simply by determining the position of the base member 81 with respect to the lower die half 90b in the longitudinal and transverse directions, or by suppressing the displacement of the cover member 82 relative to the lower die half 90b. Particularly, if the base member 81 has an elongated shape, the base member 81 is likely to be warped after injection molding. This creates variations in dimensional accuracy. When performing the in-die cover forming method using the base member 81, one end of the base member 81 is likely to separate from the lower die half 90b as schematically shown in FIG. 3. This can crease or break the cover member 82. There is therefore much demand for a technique that significantly increases the yield by suppressing defective due to variations in dimensional accuracy of the base member 81.